Unity Procject version is "Unavailable"

After Unity crashed, the project version changed to mysterious "Unavailable":

When trying to select the project's original version (2020.1.10f1), Unity crashes. Here is the log:

[1230/173655.494:ERROR:file_io.cc(90)] ReadExactly: expected 36, observed 0[1230/174605.843:ERROR:directory_reader_win.cc(43)] FindFirstFile: System cannot find the specified path. (0x3)

I have a very old copy of the project, but it is SO old that I will need to rewrite literally EVERYTHING. How I can fix that?